The reaction of N-benzoylphosphoramidic dichloride with piperidine and 4-methylpiperidine lead to PhC(O)N(H)P(O)R2 with R=piperidine (1) and R=4-methylpiperidine (2) as N-benzoyl-N′,N″-bis(piperidine) phosphoric triamide and N-benzoyl-N′,N″-bis(4-methylpiperidine) phosphoric triamide, respectively. The products have been characterized by 1H, 13C, 31P NMR spectra, and by elemental analysis. The crystalline solid for (1) and (2) consists surprisingly of four and two independent molecules, respectively. There is a disorder in one amine group due to ring inversion in each conformer in compound 1. In the solid state, comparable magnitudes for the stabilization of the stable conformers for the more or less discrete molecules, the polarization effects, hydrogen bonding and the packing effects could be anticipated.
The geometry of compound (1) optimized by density functional calculations at the B3LYP/6-31++G* (d,p) level, is in good agreement with data obtained from X-ray crystallography. 相似文献
Using the renormalization group approximation, specifically the Migdal-Kadanoff technique, we investigate the Blume-Capel model with mixed spins S = 1/2 and S = 5/2 on d-dimensional hypercubic lattice. The flow in the parameter space of the Hamiltonian and the thermodynamic functions are determined. The phase diagram of this model is plotted in the (anisotropy, temperature) plane for both cases d = 2 and d = 3 in which the system exhibits the first and second order phase transitions and critical end-points. The associated fixed points are drawn up in a table, and by linearizing the transformation at the vicinity of these points, we determine the critical exponents for d = 2 and d = 3. We have also presented a variation of the free energy derivative at the vicinity of the first and second order transitions. Finally, this work is completed by a discussion and comparison with other approximation. 相似文献
The mixed spin-1 and spin-3/2 Blume-Emery-Griffiths model with attractive biquadratic coupling is investigated in the framework of the Migdal-Kadanoff Renormalization Group method. By changing the ratio R > 0 of biquadratic and bilinear exchange interactions and according to the different values of crystal field interactions, we have determined six main types of phase diagrams. The full flow in the parameters space of the Hamiltonian was established and the fixed points obtained are drawn up in a table. In addition, we have determined the eigenvalues of the transformation of the group in the vicinity of the critical points. Finally, the introduction of a positive biquadratic interaction was discussed.
ABSTRACT In this study, we investigated the graft copolymerization of methyl methacrylate (MMA) onto low-density polyethylene (LDPE) in the presence of aniline as an inhibitor by gamma radiation. An alkaline treatment was carried out for the prepared graft copolymer. The structural properties of the prepared samples were examined via X-ray diffraction (XRD) and scanning electron microscopy (SEM). The XRD peaks were slightly shifted, indicating an interaction between MMA and the polyethylene matrix. The morphology of the samples confirmed the homogenous grafted phase scattered onto the LDPE surface. Analysis of the absorption spectra indicated an allowed indirect transition mechanism. The Urbach energy (EU) results showed that the value of the EU for grafted LDPE was found to be higher than that of pure LDPE—up to 15?kGy irradiation dose, although this value decreases upon grafting. However, the value of the EU for alkaline-treated grafted films decreases systematically by increasing the degree of grafting. The thermogravimetric analysis (TGA) of the sample indicated that the thermal stability of LDPE samples is significantly changed by grafting MMA onto it. Horowitz and Metzger's models were utilized to measure the activation energy of the thermal decomposition of all samples. 相似文献
The yield stress fluids porosimetry method (YSM) was recently presented as a simple and non-toxic potential alternative to the extensively used mercury intrusion porosimetry (MIP). The success of YSM heavily relies on the choice of an appropriate yield stress fluid to be injected through the investigated porous medium. In previous works, xanthan gum aqueous solutions were used due to their ability to exhibit a pseudo-yield stress without substantial levels of unwanted thixotropy or viscoelasticity. Given that YSM is based on the existence of a yield stress, the accuracy of the obtained pore size distribution (PSD) crucially depends on the capacity of the injected fluid to emulate the shear rheology of a yield stress fluid. However, this capacity has still not been fully assessed in the case of xanthan gum solutions. Neither has the robustness of YSM with regard to errors in the determination of the shear-rheology parameters of the injected fluid been analysed. The shear viscosity of polymer solutions is known to be deeply influenced by polymer concentration. For these reasons, a first objective of this work is to evaluate the effect of polymer concentration on the accuracy of PSDs obtained by YSM when using xanthan gum solutions as injected fluids in laboratory experiments. To do so, xanthan gum solutions with different polymer concentrations were injected through analogous samples of a sintered silicate and the obtained PSDs were compared to the results of standard MIP. Moreover, the sensitivity of YSM to errors in the experimental determination of the shear-rheology parameters was also investigated through numerical experiments. The results of the present work permitted to gain further insight into the viability of YSM as an efficient alternative to MIP. 相似文献
Nanocapsules containing hexadecane and Fe3O4 magnetic nanoparticles as core materials and polystyrene as shell were produced in a new method through emulsifier-free miniemulsion
polymerization using 2,2′-azobis(2-amidinopropane) dihydrochloride (V-50) as a water-soluble initiator. The effect of some
parameters such as the amounts of Fe3O4 and initiator on morphology of resulting nanocapsules was studied. Transmission electron microscopy showed that the products
had latex particles having a size range of about 300–1300 nanometer and both magnetic nanocapsules with core-shell morphology
and solid particles. The phase transition temperature and phase transition heat of the produced capsules were determined by
differential scanning calorimetric analyses. Thermal properties of the latex were compared with those of magneticparticles-free
latex and with those of latex free of both magnetic particles and hexadecane. Thermogravimetric analysis was also used to
confirm the encapsulation and to determine the amounts of hexadecane and Fe3O4 within the capsules. 相似文献